What is the research cost set to, and are you playing a research bonused race? How many constructors are you building?
Because so many factors effect, well, just about everything in this game, what seems like 'a lot' for me may not be much at all for you. For example, I've kept my empire's main colonies well supplied with just 4-7 constructors (started with four, now 7 of them 25 years into the game) controlled manually. I use general pirate smuggling missions for new colonies and occasional resource-specific ones when a colony runs short on something, and so far I've never felt very stretched for materials.
I think what causes stalled constructors is they pick up the resources at a colony with a small stock of something, and they don't bother to get it elsewhere before going to build. It doesn't even necessarily have to be a "shortage" at the colony because the colony may not be reserving any of that resource. The constructor tries to pick up 60 of whatever, gets the last 37, for example, and leaves.
Also, check the out your resources in the expansion planner - specifically, the "stores," "in transit," and "unfulfilled" (or something like that) columns. If your stores look reasonable but you still have a shortage, it means your private sector isn't distributing it correctly. It also could be that a good chunk of it is squirreled away on your mining stations - I've noticed a tendency of the AI to drop off 10-50 units of [insert a dozen random resources here] at mining stations. If you have a lot in transit, it looks like your private sectors is either working on the issue or just not getting it where it needs to go. Etc., Etc.
P.S. I assume you haven't played with your mining station designs. If you design your own, just make sure they have 2 mining engines (called gas extractors for gas stations I think?) and a luxury extractor each, plus a bunch of storage - I think 20 cargo containers is default.
P.P.S. That reminds me of another possible way to nuke your economy via a design flaw. Go to Ships and Bases, then Mining Stations, click the top one, then shift-click the bottom one. Now, by each mining station icon in the lower right there should be a green bar - their fuel. I think in a classic game, mining stations start with an energy collector that can usually handle their entire static energy draw, but obviously this isn't included if you start in the Age of Shadows. If you don't add one, that means higher caslon remand, lots of freighters tied up delivering fuel to mining stations, and given the AI's efficiency, possibly a lot of mining stations unable to mine.